The invention relates to paint color changers for paint application systems. More particularly, the invention concerns a powder paint color changer adapted for use with paint application systems utilizing solid particulate paint particles entrained in a fluid such as air.
Paint color changers are known in the art for both liquid and powder paint applications. In liquid paint applications, the color changers are positioned as closely as possible to the paint application apparatus to save on solvent and paint waste. For powder applications, it has been found better to place the color changers closer to the source of the powder paint rather than to the application device.
In the typical powder paint application, pressurized air is used as a diluter and carrier of the powder paint particles to the application device via a color changer. Unlike the liquid paint application, powder applications do not utilize cleaning solvents. The transport air is a neutral means of transporting the powder such that the powder paint is very diluted in the hoses connecting the various apparatus of the system, and its amount is relatively small. These characteristics are what suggest placing the powder color changer closer to the feed hoppers rather than as close as possible to the paint applicator as is the case for liquid paint applications. This feature helps to reduce the number and length of powder feeding hoses in a multiple color system.
In prior art powder paint color changers, such as those disclosed in U.S. Pat. No. 4,302,481 to Ribnitz, et al., where multiple colors enter a common color changing manifold, separate air purging channels are required for each manifold powder paint input. This complicates the color changing arrangement thereby adding expense.
Another problem with powder paint applications is the phenomenon known as impact fusion. Impact fusion occurs where the particles of powder paint encounter surfaces in prior art color change manifolds having relatively high friction surfaces thereby leading to powder particle agglomeration and adhesion to the color changer surfaces. Such adhesion, in turn, leads to problems in both cleaning of the apparatus prior to changing colors and may, over time, lead to inoperativeness of the color changer due to clogging of various passageways therein.
Therefore, there is seen to be a need in the art for a color changer for powder paint applications providing facile cleaning and resistance to particulate impact fusion at powder paint carrying surfaces therein.
In accordance with the invention, a powder paint color changer has a hollow body portion having first and second opposed ports at its outer surface, the first port adapted to be coupled to a source of cleaning fluid and the second port adapted for coupling to a powder paint application device. A plurality of valves, each having an outlet in fluid communication with an interior cavity of the hollow body portion and each having an inlet adapted to be coupled to a different source of powder paint are each operative in a first state to enable fluid communication between a valve inlet and a valve outlet and operative in a second state to prevent fluid communication between the valve""s inlet and outlet.
In another aspect of the invention, a powder paint color changer is of a two-piece construction wherein a replaceable or a nonreplaceable insert fashioned from a material resistant to impact fusion of powder paint particles with a surface of the insert is positioned within the color changer such as to define an interior cavity thereof. A plurality of valve elements are coupled to the color changer and are in fluid communication with the interior cavity formed by the replaceable insert.